Although on most systems va_end is a no-op, it is good practice to use
va_end on the function return path, especially since the va_start
documenation states:

  "Each invocation of va_start() must be matched by a corresponding
   invocation of va_end() in the same function."

Found with static analysis by CoverityScan, CIDs 1389477-1389479
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Manish Rangankar <manish.rangankar@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>